linux-kernel - [PATCH v2] genalloc: Make the avail variable an atomic_long

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Message-Id: <1509033843-25667-1-git-send-email-sbates@raithlin.com>
Date:   Thu, 26 Oct 2017 10:04:03 -0600
From:   sbates@...thlin.com
To:     corbet@....net, sbates@...thlin.com,
        mathieu.desnoyers@...icios.com, danielmentz@...gle.com,
        akpm@...ux-foundation.org, will.deacon@....com,
        linux-kernel@...r.kernel.org, logang@...tatee.com
Subject: [PATCH v2] genalloc: Make the avail variable an atomic_long_t

From: Stephen Bates <sbates@...thlin.com>

If the amount of resources allocated to a gen_pool exceeds 2^32 then
the avail atomic overflows and this causes problems when clients try
and borrow resources from the pool. This is only expected to be an
issue on 64 bit systems.

Add the <linux/atomic.h> header to pull in atomic_long* operations. So
that 32 bit systems continue to use atomic32_t but 64 bit systems can
use atomic64_t.

Changes since v1:
  Change atomic64 to atomic_long as per Mathieu
  Added a Reviewed-by tag from Logan

Signed-off-by: Stephen Bates <sbates@...thlin.com>
Reviewed-by: Logan Gunthorpe <logang@...tatee.com>
---
 include/linux/genalloc.h |  3 ++-
 lib/genalloc.c           | 10 +++++-----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
index 6dfec4d..872f930 100644
--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h
@@ -32,6 +32,7 @@
 
 #include <linux/types.h>
 #include <linux/spinlock_types.h>
+#include <linux/atomic.h>
 
 struct device;
 struct device_node;
@@ -71,7 +72,7 @@ struct gen_pool {
  */
 struct gen_pool_chunk {
 	struct list_head next_chunk;	/* next chunk in pool */
-	atomic_t avail;
+	atomic_long_t avail;
 	phys_addr_t phys_addr;		/* physical starting address of memory chunk */
 	unsigned long start_addr;	/* start address of memory chunk */
 	unsigned long end_addr;		/* end address of memory chunk (inclusive) */
diff --git a/lib/genalloc.c b/lib/genalloc.c
index 144fe6b..ca06adc 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -194,7 +194,7 @@ int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phy
 	chunk->phys_addr = phys;
 	chunk->start_addr = virt;
 	chunk->end_addr = virt + size - 1;
-	atomic_set(&chunk->avail, size);
+	atomic_long_set(&chunk->avail, size);
 
 	spin_lock(&pool->lock);
 	list_add_rcu(&chunk->next_chunk, &pool->chunks);
@@ -304,7 +304,7 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
 	nbits = (size + (1UL << order) - 1) >> order;
 	rcu_read_lock();
 	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
-		if (size > atomic_read(&chunk->avail))
+		if (size > atomic_long_read(&chunk->avail))
 			continue;
 
 		start_bit = 0;
@@ -324,7 +324,7 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
 
 		addr = chunk->start_addr + ((unsigned long)start_bit << order);
 		size = nbits << order;
-		atomic_sub(size, &chunk->avail);
+		atomic_long_sub(size, &chunk->avail);
 		break;
 	}
 	rcu_read_unlock();
@@ -390,7 +390,7 @@ void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
 			remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
 			BUG_ON(remain);
 			size = nbits << order;
-			atomic_add(size, &chunk->avail);
+			atomic_long_add(size, &chunk->avail);
 			rcu_read_unlock();
 			return;
 		}
@@ -464,7 +464,7 @@ size_t gen_pool_avail(struct gen_pool *pool)
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
-		avail += atomic_read(&chunk->avail);
+		avail += atomic_long_read(&chunk->avail);
 	rcu_read_unlock();
 	return avail;
 }
-- 
2.7.4